Backing paper for roll photographic film



July 21, 1953 E. L. BAXTER 5 3 BACKING ?AFER FOR ROLL PHOTOGRAPHIC FILM Filed Dec. 8, 1951 ;5 ZEN PROTECT/ON" PRINT/NG W/////I/I///l//I//I/I/I//I/I ZE/N-YELLOW PA PER i POLYV/NYL ACETATE v \&\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ RBO/v BLACK ZE/N-CARBON BLA CK V Ernest LBaxt'er INVENTOR.

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Patented July, 21, 1953 'UNITED I STATES' -PATENT OFFICE BACKNG PAPER FORBOLL PHOTOGRAPHIC Ernest L. Baxter, Rochester, N. Y., assjignor to Eastn Kodak Company, Rochester, N. Y.`, 'a

corporaton 'of New Jersey --pplication'Dece'niber 8, 1951 SefiaLNJOli The 'hacking 'paper of this invention is an 'im pro'vement 'over that described 'and claimed in my copending patent 'application ser. 18' 7,124, filed September 27, 1950.

'2 ciamsi (Cl. In 14:)

' As is well understood, a photographic roll film cartridge generally comprises a flang'ed spool upon which is wound a long strip of hacking paper to which before winding has been attached a strip of lig ht sensitive photographic film. The ends of the hacking paper are positioned to extend beyond the ends of the film and constitute light protective leader and trailer strips for 'the film which is interwound with the hacking paper and, 'therefore, separates adjacent convolutions i of the film.

In' a commonly available roll film Cartridge, the film is attached to the black side of a duplex hackin paper, the side of the 'hacking paper op*- posite that contacting the film is difierently colored and carries various printed symbols such as the number of the exposed areas, waming marks, and advertising matter, over which is coated a protective layer intended to protect the sensitive emulsion from the paper and ink employed in printing when the film and paper 'are interwound in close contact. It has been the practice to depend somewhat on the paper itself `'to'preven't the transmission 'of light'. 'o assure opaqueness, hacking paper presently e'mployed for roll films generally consists of a duplex paper with one 'side being black and the other side colored with a characteristic identifying color. The paper may he made 'by means of a Fourdinier paper machine and 'a cylinder paper machine. The two sheets are'hrou'ght together wet under the first press and thus form a single composit'e sheet of hacking paper.

Duplex hacking paper has certain 'defirite specifications that must be met. The black side must be' opaque` and free from pinholes. 'The lighter colored side should be uniorm in color and appearance and should not permit any' of the black on the opposite 'side to he visible through the paper. The diameter of the finished spoo of roll film, and, therefore, the number of exposures, is dependent on'the overall thickness v iz of the hacking' paper"and the film, s'o thickne'ss of the paper itselfunust he limited. The required 'streng'th "of 'the paper' which i important both in the 'camera 'and' processing, "also limitsxthethinness 'of the paper. Either hlacknumerals'or a :white paper or white numerals -on a ;black "paper give the greate'sft ccntrast, 'but neither paper 's ;ver pleasing; to the eye. Light er colored backgrounds such asshadesqf red, green,

yen'ow' and blu e are mostflesirahle from an apde no 'a';ppea

in current use; wfin will 'f ulfill the necessary requirements of such a paper.` In order that the sheet may be phtgraphiclly paque, a certain minimum Weight and thickness of black is requred. The l'ihter' the shade and color of the other side, theg're'atr 'is 'the weight and thickness of paper reduired thde thhlak side and to give the light colored side a' uniform appearan ce. The presentinvention, howeven provides a thinner hacking paper which does not have a duplex structure but which has superior charact ri vtics., e

Anohject, therefore, of the present invention is' to provide@ ac ingpa er o i n in sheet of paper, as contrasted to a duplex paper, whichhas a strength at least equal to the thin' :fest duplex papers now .produced.

Another object of, theinvention is to 'provide a single sheetcoated hacking paper which -i's'not only thinner than present duplex paper, but has an opaqueness superior to duplex hacking papers.

Another object of the present invention is to providera. thinisingleisheet hacking paper, the opacity of whichis dependeritpr'marily on the Chemical coating onthe ..paper rather than the paper structure itself.

'Still another object is to ,provide a hacking i other ohje'cts ar attmed by 'employing' 'asjthe aper 'stripin the backin'g paper a "sing'1"she`e`t,-

as cotr'asted to aduplex paper,`whch has been "pussy-s -o a paper nan to' make-'a plx back g "pa er thinner' 'than those supercalendered to a thickness appreciaby less than commonly employed duplex papers. By itself this paper is so thin that it transmts sufllcient actinic light to cause film exposure. This single paper is then coated on one side with one or more black opaque coatings and on the other side by a compositecoating of lighter colored composition. The paper may then be printed on the lighter colored side and, if so printed, the printed side is given a protective overcoating to protect the film emulsion from the printing inks. The various coatings may be applied in proper sequence by a rotogravure process or by other suitable coating processes. ;The coatings may be suitably dried between applications. i p

The paper preferably employed as the base of the backing paper structure is a l-pound per 1000 sq. ft. paper made of a puried fiber 'or of unpurified fiber such as unbleached kraft paper which is conditioned to 442% moisture content and supercalendered to a thickness of 0.0025 to 0.0030 inch. This thin paper is then coated on one side with a plurality of black coatings. The opposite side of this thin paper is coated with a yellow coating. The composition of the black and yellow coatin is described hereinafter. The thus coated paper is printed on the yellow side with suitable legends and overcoated with a protective coating of a prolamine to protect the film emulsion from the printing inks when the film and hacking paper is rolled onto the film spool.

The following colored coating compositions are preferred for use in preparing a backing paper in accordance with my present invention:

Initial black coatings In the above formulas, titanox represents a finely. divided titanium pigment; medium chrome yellow is a finely divided metal chromate pigment; light orange is a finely divided metal chromate pigment, and the carbon black pigments are similarly finely divided. Zein is employed as the binder in the yellow and final, black coating since it will not fog or desensitize the photographic emulsion of the film.

A suitable rotogravure process for applying these coatings to the paper base of the backing paper is described in U. .S. Pat'ent 2,218,249 of October 15, 1940. The various applications are made continuously and each coating is dred before the next is applied. The coating is applied to the paper by the intaglio roll which is rotatably mounted in a pan containing the coating solution. The surface of the roll is embossed providing a plurality of very minute cups which carry the solution, the excess solution being removed from the roll by a doctor blade. The solution in these various cups is then transferred or applied uniformly to the strip by pressing the strip against the cups by means of a rubber pressure roll over which the strip is fed. Each of these deposits after being placed on the paper is merged into a continuous layer by means of a smoothing bar to provide a uniform coating over the entire paper surface. Each coating is preferably dried in heated air having a relative humidity of 6% at F. before applying a second coating.

suitable ink compositions for printing indicia by rotogravure processes on the backing paper are disclosed in my Patent Re. 21,268 of November 21, 1939. These inks comprise suitable color ing materials in a prolamine binder such as zein. Other suitable coatings for such backing papers are disclosed in my Patent 2,262,936 of November 18, 1941.

The invention will be further understood by reference to the drawings in which Fig. 1 represents a greatly enlarged cross-section of backing paper made in accordance with my present invention, and Fig. 2 shows the backing paper and photographic film wound on the roll with the film and paper separated at one end for purpose of illustration.

Referring to Fig. 1`, a strip of unbleached kraft paper is shown at 10 having a coating ll of a layer of carbon black in a polyvinyl acetate binder thereon which is overcoated with a layer of carbon black in a zein binder. On the opposite side of the paper !0, there is the yellow coating !3 comprising orange and yellow pigments as wel as titanium dioxide pigments. The printed indicia is shown at IB overooated With a protective zein coating I 5. such a protective coating is described in my Patent 2,262,987 of November 18, 1941.

Referring to Fig. 2, a film Cartridge 20 is shown partly open in which the backing paper of the present invention is employed. This figure shows the relation of the backing paper surfaces l I and !5 in respect to the film ZI when assembled on the spool. The emulsi-on side of the film is shown at 23 and the pelloid side at 22.

I have found that by employing an initial coating of carbon black in polyvinyl acetate, which is overcoated with carbon black in zein on the black side of the paper, the resulting oack'ng paper structure has considerable improvement in respect to flexibility of the black side without loss of resistance to scratching and abrasion. In this respect the hacking paper of the present invention is superior to that described and claimed in my copending application Ser. No. 181124, supra.

, The polyvinyl acetate binder coating is less brittle than a zein coating of a corresponding thickness.

However, with the thickness of the zein coating heretofore required reduced by the polyvinyl acetate coating, the remaining zein overcoating is thin and flexible enough to withstand the bendng of the backing paper while at the same time providing an abrasion resisting layer over the softer polyvinyl acetate.

While the preferred coating compositions are described above, satisfactcry backing papers may 55 i r b'emad'e zby employing the zvarioisaieting :ma terials in the followingianges: 'auf i Preierred Compostons V Range 'v J I fier cent' Zein 7 to 25. Polyvinyl acetate to 25. Black pigmentl to 1 5.

otherjuseful pigments are, for example, Hansa Yellow, Fast Pigment Yellow and any carbon black 'of suitable dispersion.

Other pigments which are inert to photographic emulsions may be employed. In fact, any 'choice of pigments of suitable size for this invention is limited only by the requirement that they be without detrimental efiect on the photographic film.

Th'ckness of coat'ng Black coating composition is applied in four coatings to give a total of 12 lbs. of solution per 1000 sq. foot for satisfactory opacity. p

Light pigment composition is applied in the amount of 4% lbs. per sq; foot to give satisfactory uniformity of color. V

Any other type of paper may be employed if it has good strength at' least comparable to the present duplex paper. A rag paper, for example,

' is suitable but, of course, more expensive than kraft paper.

Comparson of uplex and kmft tear strength g Schopper Folds Along Across Along Across Gms. Gms. Typical Duplex Paper 70 84 410 28 Tan Krait Paper (as employed in the present invention) 65 v 75 475 100 Preferably the average tear strength of a suitable paper should be at least 50 grns. as determined by the Elmen'dorf tear test. This tear test is dev scribed in Paper Trade Journal for June 18, 1942,

as Tappi Standard T414 M40.

While polyvinyl acetate is the preferred binder for the opaquing coating, other binders may be employed in its place such as vinylidene-vinyl chloride polymers such as "Geon or "Saran" and the butadiene-styrene type polymers such as Dow Latex. These polymers may be applied as latces as well as from solvent solutions. The following composition illustrates such a suitable alternative op-aquing medium y Pounds Saran latex 133 Aquablak B 100 Water 29 The Saran latex contains 525% solids and the i Aquablak B is a 35% dispersion of carbon black in water.

u whileas indicatedab-ove, tan ikrat paper is particularly s'uited *for 'employmen't in my inve'n tion, certain. .other types o'f paper could be emiployed instead, 'suchasunbl'eached sulf ate paper .coloredwith asuitabledyetsu'chtas *Stilbene-*yllow in whicha small amount of llersuch :as ?12102215 added to give rbo'dyfand densit'y 'pr opacityeto !the v ipaperhw,

These papers cbmprising the. base of *the lbacking-.paperzarero asweig'htthat can be -supercalendered to' asthinness :that :the 'paper itself plus th-e coatings-thereon does not exceed tavlmaximum thiclmess ot o-;oo lo inch ;A l-vpound per Msq. ft.pa'per has been founcllsatisfactory.

The opacity otroll film .backingpape'r is :tested in the following manner.

A sheet of the hacking paper under test is placed over a sheet of highly sensitive film, such as Super XX Panchromatic Film with the black side of the' hacking paper in contact with the back of the film, duplicating its position on roll film. An orange-red filter of the type employed duplex papers which it may replace. The strength and other physical properties of the paper employed as the base of the backing paper is at least equal to the strength of the thinner duplex papers now available to the trade. The overall thickness i can be m ade as low as 0.0032 up to 0.0040 inch thus permitting extra vexposures to be added to present rolls of film without increasing the diameter beyond that of films now in use. The

i opaqueness, even though the overall thickness is less than hacking papers now available'in the trade, is better than such backing papers. The backing paper made in accordance with my invention requires the least amount of coating materials, both black and colored, of any of the methods described or known in the trade. The

' uniformly light colored side gives maximum contrast with the legends printed thereon. Also less clock springing of freshly rolled film is experienced with this paper than with'the thicker duplex paper. These advantages plus the advani tages of applying the coatings by rotogravure methods, which are fast, accurate and efficient; emphasizes the importance of my present invention in this art.

What I claim and desire to secure by Letters Patent of the United States is:

1. Photographic backing paper having an overall thickness less than 0.0040 inch comprising a single sheet of kraft paper, as contrasted to a multiple sheet of duplex paper, of a thickness of approximately 0.0026inch which will permit passage of substantial amounts of actinic light, having on one side an opaquing coating compri'sing carbon black in a polyvinyl acetate e binder which is overcoated with a second opaquing 'coating comprising carbon black in a zein binder, a lighter colored pigmented coating oni the opposite surface of the paper comprising a yellow pigment in a zein binder, printing on said lighter 'colored coating, and a clear zein protective coating thereover, the complete backng paper being suificiently opaque to prevent actinie light from passing therethrough.

&646366 2. Photographic hacking paper having an overall thickness less than 0.0040- inch eomprising a single sheet of tan kraft paper, as contrasted to a, multiple sheet of duplex paper, of a thickness .of approximately 0.0026 inch which will permit passage of substantial amounts of actnc' light, having on one side an opaquing coatng comprsng carbon black in a polyvinyl acetate binder which is overcoated With a second opaquing coating comprisng carbon black in a zein' binder, a lighter colored pigmented coating on the opposte surface of the paper comprising a yellow pigment in a zein binde', printing on said lighter colored coating and a clear zein protectve coatng thereover, the complete backing paper 15 2,157,206

being sufilciently opaque to prevent actinic light rays from passage therethrough.

ERNEST L. BAXTER.

References cited in the file of this patent UNITED STATES PATENTS 10 Number i Name Date 1,481,529 Baltz' et al Jan. 22, 1924 1,614,490 Poorman Jan. 18, 1927 1,820,168 Vehl et al. Aug. 25, 1931 1,954,333 Sheppard et al Apr. 10, 1934 Hinman May 9, 1939 

1. PHOTOGRAPHIC BACKING PAPER HAVING AN OVERALL THICKNESS LESS THAN 0.0040 INCH COMPRISING A SINGLE SHEET OF KRAFT PAPER, AS CONTRASTED TO A MULTIPLE SHEET OF DUPLEX PAPER, OF A THICKNESS OF APPROXIMATELY 0.0026 INCH WHICH WILL PERMIT PASSAGE OF SUBSTANTIAL AMOUNTS OF ACTINIC LIGHT HAVING ON ONE SIDE AN OPAQUING COATING COMPRISING CARBON BLACK IN A POLYVINYL ACETATE BINDER WHICH IS OVERCOATED WITH A SECOND OPAQUING COATING COMPRISING CARBON BLACK IN A ZEIN BINDER, A LIGHTER COLORED PIGMENTED COATING ON THE OPPOSITE SURFACE OF THE PAPER COMPRISING A 